In general, with development of mobile communication, use patterns of and demands for a communication device of users have been diversified. Users wish to perform communication without time and space restriction. However, an output from a base station is restricted, and thus, a shadow area may exist due to the location of a base station or the topography of an area. In order to eliminate the shadow area, a distributed antenna system is used.
The distributed antenna system includes a headend device coupled to the base station and a remote device coupled to the headend device through an optical cable. The distributed antenna system is installed in an area in which a radio wave is not received or is weak, such as the inside of a building, the basement of a building, a subway, a tunnel or an apartment complex of a residential area. The distributed antenna system is used to extend the coverage of a base station such that a service is provided to a shadow area which a signal of a base station is unlikely to reach.
For example, in the case of the downlink among the services provided by the distributed antenna system, the headend device serves to combine signals received from the base station and then convert the signals into an optical signal thereby transmitting it to the remote device, and the remote device restores the received optical signal to the original signal and amplifies the restored signal thereby transmitting it to a terminal.
At this time, the higher the signal-to-noise ratio (SNR) of an optical signal transmitted to the remote device from the headend device, the more the quality of the service is improved. However, since there is a limit in increasing the power of a signal to improve the signal-to-noise ratio to increase the power of the signal, the power level of the signal, that is, the transmission resource is limited. For that reason, in the case where various base station signals are combined to be transmitted as an optical signal, there is a problem that the distributed antenna system for providing a multi-band service should distribute appropriately the transmission resource for each of the base station signals so that the base station signals each are transmitted with an optimized power.
In a conventional distributed antenna system, a technician directly analyzes, by using a measuring instrument in the field, signals inputted to the distributed antenna system, and then distributes the limited transmission resource in a manner of controlling attenuation for each signal. However, according to the conventional art, since the technician in the field often performs the repeated optimization of the transmission resource distribution of the distributed antenna system according to his ability, there is a problem that a lot of manpower and time is required.
An object of a headend device of a distributed antenna system and a signal processing method thereof according to the technical features of the inventive concept is to efficiently optimize and thereby distribute a transmission resource of a distributed antenna system for each of signals, and aim at the convenience of an administrator.